Rheostat.



No. 649,927. Patented May 22, I900.

C. FLOHR GL R. DIETZE.

BHEDSTAT.

(Application filed. July 3, 1899.)

(No Model.)

a J j v f g A UNITED STATES PATENT OFFICE.

CARL FLOUR, OF BERLIN, AND REINHABD DIETZE, OF COSXVIG, GERMANY.

RH EOSTAT.

SPECIFICATION forming part of Letters Patent No. 649,927, dated May 22, 1900.

Application filed July3,1899. Serial No. 722,712- iNo model.)

To all whom it may concern.-

Be it known that we, CARL FLOHR, of I3erlin, and REINHARD DIETZE, of Goswig, Germany, have invented'certain new and useful ImprovementsinRheostats; and we do hereby declare the following to be a full, clear, and exact description of the invention, such as will enable others skilled in the art to which it appertains to make and use the same, reference being had to the accompanying drawings, and to letters of reference marked thereon, which form a part of this specification.

The rheostats hitherto employed for highpotential currents and comprising a mass of pulverulent resisting material, into which a regulating contact-piece is dipped to a greater orless depth,are attended by the disadvantage that when they are being operated the metallic powder sticks to the insulating portions of the apparatus, whereby paths are made for the current that cause short circuits and disturbances of working. This disadvantage is obviated according to the present invention by means of a special sliding contact device that is connected with the regulating contact-piece and by means of which, for the sake of safety, the circuit is again broken after the regulating contact-piece has passed out of contact with the mass of resisting material; but that our invention may be fully understood we will describe the same in detail, reference being had to the accompanying drawings,in which- Figures 1 and 2 are vertical sections of a rheostat embodying ourinvention and showing the contact-arm in different positions. Fig. 3 is a cross-sectional view thereof, the contact-arm B being removed from its spindle; and Fig. l is a left-hand elevation of Fig. 3.

In the drawings, A indicates a suitable closed box or receptacle made of a non-conductive material and having hearings in two of its opposite sides at a suitable elevation for a spindle G, of conductive material, carrying within the box a radial conductor or contactarm B and on the outside of said box a contact-arm c. In the path of the contact-arm B, within the receptacle, is arranged a contact-spring 0, connected to a binding-post H, to which is connected the negative pole of an electric circuit, and on the outer face of the box A is arranged a fixed conductor or contact in the form of a segmental plate a, con centric with the spindle G, and a small plate 19, both in the path of contact-arm c, said co1i-' tact-plate a being connected by wire F to a binding-post E, to which is connected the positive pole of the electric circuit.

The box A is partly filled with a pulverulent metallic resistance material m, and the contact-arm B is so arranged on its spindle G that by suitably rotating the latter by means of the crank b the said arm is caused to penetrate into said resistance material to a greater or less extent and to thereby vary the degree of resistance to the passage of the current, while when said spindle is turned to move the arm out of the resistance material the contact-arm a will lie on plate I) and the rheostat will be cutout of the circuit.- When the contact-arm B is in the position shown in Fig. 1, for instance, current flows from E via F to fixed contact a, trailing contact 0, spindle G, resistance material at, contact-spring C, and negative binding-post H. If, on the contrary, the spindle G is turned to bring the conductor-arm B in direct contact with spring 0, Fig. 2, then current will flow as before to said contact-arm B and thence direct to spring 0, thus forming a short circuit and cutting the resistance out, as will be readily understood.

The relative radial position of the contactarm B and the trailing contact 0 on spindle G is such that when in their normal positions the said trailing contact 0 lies in advance of contact-arm B in the direction in which the spindle G is to be turned to move the said arm B into the resistance material at to a greater or less extent, and the arrangement of the contact-plate a is such that the trailing contact 0 will contact with said plate a before the contact B comes into contact with said resistance material, the reverse taking place in switching the rheostat out of the circuit. The arm B will move out of contact with the resistance material or before contact 0 breaks contact with a, thereby avoiding the difficulties above referred to.

Having thus described our invention, what we claim as new therein, and desire to secure by Letters Patent, is

1. A rheostat comprising two stationary contacts insulated from each other, one of said contacts consisting of a resistance material, in combination with two movable contacts cooperating with said stationary contacts, and means for shifting said movable contacts so that one will contact with the resistance material after the other has made contact with its stationary contact, for the purpose set forth. 7

2. A rheostat comprising two stationary contacts insulated from each other, one of said contacts consisting of a resistance material, in combination with two movable contacts cooperating with said stationary contact-s, and means for shifting said movable contacts so that one will contact with the resistance material after the other has made contact with its stationary contact, and so that in reversing the motion of said movable contacts they will break contact with their respective stationary contacts in reverse order, for the purpose set forth.

A rheosta-t comprising two stationary contacts insulated from each other, one of said contacts consisting of a comminuted resistance material, in combination with two movable contacts one of which is adapted .to be moved to a greater or less extent into said resistance material, and means for shifting the movable contacts so that one will contact with or enter into the resistance material after the other has made contact with its stationary contact and so that in reversing the motion of the movable contacts they break contact with their respective stationary contacts in reverse order, for the purpose set forth.

' 4. A rheostat comprising two stationary contacts insulated from each other, one of said contacts consisting of a resistance material, in combination with two movable c011- tacts cooperating with said fixed contacts,

means for shifting said movable contacts so that one will contact with the resistance material after the other has made contact with its fixed contact, and means for short-circuitin g the movable contact which cooperates with the resistance material and cut the latter out of circuit, for the purpose set forth.

5. A rheostat comprising two stationary contacts insulated from each other, one of said contacts consisting of a comminuted resistance material, in combination with a movable contact cooperatin g with and adapted to penetrate to a greater or less extent into the resistance material, a movable contact cooperating with the other stationary con tact, means for shifting said contacts so that one will contact or enter the resistance after the other makes contact with its stationary contact, and means for short-circuiting the movable contact that cooperates with the resistance while in contact therewith, for the purpose set forth.

6. A rheostat comprising a boX, a com min uted resistance material partly filling the same, the spring 0 partly embedded in said material and the segmental contact-plate a and the contact I) on the outside of the box, in combination with the conductive spindle G, the radial contacts B c thereon, and means for circuiting the aforesaid spring O and contact a, said parts arranged relatively to one another and operating substantially as and for the purpose specified. 

